Ablation resistance of carbides-coated C/C composites

Abstract

To improve the ablation resistance of C/C composites under oxyacetylene flame, SiC, TaC and HfC coatings were fabricated on composites surface. Ablation properties of coatings were detected and the ablation mechanism was discussed in the paper as well. The centre region of SiC and TaC coatings has failed during ablation and exhibited high ablative rates; it attributed to so high ablation temperature, which was much higher melting point of their oxides (Ta 2 O 5 and SiO 2 ). HfC coating exhibited lowest ablative rates. The reason is that the ablation temperature was just between sinter point and melting temperature of HfO 2 , the oxides could behave as the thermal barrier coating during ablation and provide efficient protection for C/C composites. It can be indicated that the carbide coating provides best ablation protection between the Tammann temperature and melting point of their oxides.

Effect of Al2O3 and SiO2 Inert-Fillers on the Microstructural Evolution and High Temperature Oxidation Resistance of B Modified Silicides Coatings Prepared by Pack Cementation Technology

“…The formation mechanism of HfO 2 was similar to the internal oxidation of Nb-Si based alloys, the oxidation process of which was also governed by the inward diffusion of O [9]. HfO 2 has higher melting point (2800 • C) than that of pure SiO 2 [32]. Thus, the dispersion of HfO 2 in SiO 2 glass could increase the melting temperature of the silica.…”

Ablation behaviour of ZrC coating by novel solid shielding/shrouded plasma spray

“…[3,11]. The linear and mass ablation rates of the samples (after 60 s) were calculated from Equations (1) and (2): where Rl and Rm are the linear and mass ablative rates, respectively; d0 and d1 are the thicknesses of the centre of the sample before and after ablation, respectively; m0 and m1 are the masses of the sample before and after ablation, respectively and t is the ablation time [26].

Figure 3 Supersonic flame ablation test setup designed at Malek Ashtar University of Technology (MUT).

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“…where Rl and Rm are the linear and mass ablative rates, respectively; d0 and d1 are the thicknesses of the centre of the sample before and after ablation, respectively; m0 and m1 are the masses of the sample before and after ablation, respectively and t is the ablation time [26].…”